Method for shooting oil wells



March 3, 1953 R. L.. KLOTZ, JR 2,630,182

METHOD FOR SHOOTING OIL WELLS Filed Feb. 19, 1947 2 SHEETS- 51mm 1 INVENTOR.

March 3, 1953 R. L. KLoTz, JR 2,530,182

METHOD FOR SHOOTING OIL WELLS Filed Feb. 19', 1947 2 SHEETS-SHEET 2 IN VEN TOR.

iatented Mar. 3, 1953 UNITED STATES TENT QFFICE METHOD FR SHOOTING OILWELLS Application February 19, 1947, Serial No. 729,657

2 Claims. l

The present invention relates to improved methods and apparatus forshooting oil Wells either to increase the primary productivity there.-of or to facilitate stripping wells in old fields.

In general, oil Well shooting falls into two classes, i. e., shootingnew producing Wells to increase primary production and the shooting ofwells in old depleted elds to permit Well stripping after primaryproduction has stopped, In the first case, the object of. shooting awell is to render a formation believed to be oil-bearing, more permeableby cracking. and breaking up the formation material` from the holeoutward through the side Walls of the formation and into the formation.This has the eiect of increasing or facilitating the flow of oil fromthe oil=bearing formation into the well. Shooting to increase theprimary production in deep wells is yusually aocomplished by depositinga torpedo loaded with nitroglycerine, blasting gelatin or the like,alongside the oil-bearing` formation with a time bomb; fluid, sand orcement tamping the torpedo; and then letting the time bomb detonate theexplosive torpedo charge after the tamping operation is completed. Inshallow well shooting, fluid tamping is usually used andv detonation oithe torpedo charge is effected by using jack squibs, "torpedo bumpers orelectrical facilities instead of time bombs. Thesize of the explosivecharge used in shooting wells to increase primaryV production may rangefrom one hundred pounds to two thousand pounds or more, depending uponthe thickness of the probable producing formation and the character(hardness) of the formation. 'I'he second generall class, wellstripping, is often carried out by drilling water wells at pointssurrounding the well or by using former oilv/ells which surround the oilWell but have turned to Water. These water wellsare then used to forceWater under pressure intothe oil bearing forma..- tion so that the oil`is lifted, up-structure and flows into the hole. 1urtherthe4 forcing ofWater into the formation has the eiect of maintaining the bottom holepressure. This is known as water flooding. Here the increase of.' oilnow is augmented by shooting the water Wells as Well as the oil wellitself.

Experts in the art of Well shooting all agree .that ,in shooting a welleither to increase primary production or to strip the, Well, it isdesirable to crack the formation material as far out from the side Wallsof the well. as possible. They also agree that in shooting the Waterwells surrounding an oil Well to be vstrippechit isdesirable to crack=the formation material as far as' possible toward the 2` oil bearingpart of the formation, but not to crack the formation material indirections away from the oil Well since this increases the amount ofWater pumping which must be done in order to lift the oil into the Well.It is also desirable to avoid increasing the permeability of so-calledby-passing sands Which may overlie the oilbearing formation and reducethe efliciency of the Water pumping operation by absorbing Water.However, conventional shooting techniques do not permit suchdirectionalized shooting. Moreover, there is serious doubt as to whetheror not conventional shooting methods accomplish any cracking of theformation material. Thus many experts believe that since the explosiveenergy is uniformly dissipated in all directions radially outward from'the well bottom, the only effect obtained is that of enlarging the holeby compressing theadjacent formation material. Such compression may havethe effect of actually decreasing `the porosity of the formationmaterial instead of increasing it as desired. Regardless of the validityof this contention, it is denitely established that substantialcrackingof the formation material (as measured in terms of increased Wellproduction) can only be obtained through the use of 'excessivequantities of explosive material.A

It is an object of the-present invention, therefore, to` provide animproved method and improved apparatus for shooting oil Wells toincreasethe productivity thereof, which obviates the above-describeddisadvantages. of prior art methods and apparatus used for the samepurpose.

It is anotherobject ofthe invention to provide an improved method andimproved apparatus for shooting an oil well and a group of surroundingWater Wells ined in pressurized water flooding of the oil-bearing:structure to effect an extensive cracking of the oil-bearing formationmaterial in the oil well inV all directions and to eifect an esn tensivecracking of the same` formation (but water-bearing) in the water wellsin directions oriented` towards the oilwell (and not in otherdirections) Whose now it is desired to increase or whose pressure `is tobe maintained.

It is still another and more specific object of the invention to provideimproved apparatus of the character described which is of low costconstruction, minimizes `the amount of tam'ping required, and provides`for highly efficient utiliza-- tion of the. explosive material embodiedtherein.

The invention, both as to its organization and method of operation,together with further objects thereof, will best be understood byreference to the following specification taken in connection with theaccompanying drawings in which:

Fig. 1 is a fragmentary sectional vieu7 taken along a vertical planeextending downward from the surface of the earth illustrating the mannerin which the present invention is employed to` shoot an oil Well andsurrounding water wells for the purpose of stripping the oil-bearingformation into which the oil Well extends;

Fig. 2 is a top plan view illustrating the pattern of the oil well andsurrounding water Wells;

Fig. 3 is a fragmentary sectional View illustrating the details of oneembodiment of the present Y Vim'preved apparatus for shooting Ytheoil-'Weil Y shown in Fig. 1; Fig. 4 is a sectional view taken along thelines figuration of the device shown in Fig. 3;

Figs. 5, 6, 7 and 8 are sectional views illustrat- I trating amodification of the device shown in Fig.

3; and

Fig. 12 is a sectional view taken along the lines I2-I2 in Fig. 11.

Referring now to the drawings and more particularly to Figs. 1 and 2thereof, the present invention is there illustrated in its use to crackthe subsurface oil-bearing formation material in an old depleted oilwell I@ which is to be stripped by the water flooding method referred toabove. More specically, the well It extends from the surface of theearth downward into an oil-bearing formation II in the earths crust. Toflood this formation for the purpose of lifting the oil therein andcausing the same to rise in the bottom of the Well Iii, a plurality ofWater wells I2` are drilled in the earth at points radially displacedfrom .and surrounding the Well I to a depth slightly greater than Vthedepth of the oil-well, i. e., into the water-bearing part of theformation iI. As explained above, in order to increase the iiow of oilfrom the structure Il into the bottom of the Well I0 and to force the`water (introduced into the Wells l2 under pressure by suitable pumpingequipment, not shown) to flow into the oil-bearing portion of theformation I I, it is highly desirable to crack up the formation materialdisposed betwen the well l0 and the water wells I2.

In accordance with the present invention this is accomplished bydepositing at the bottom of the oil well III an explosive charge I3having cavities along the sides thereof which have the effect ofconcentrating and directing radially outward from the longitudinal axisof the well the explosive forces developed upon detonation thereof, anddepositing additional charges Ici at the bottoms of the water Wells I2having cavities therein generally facing the oil Well Iii which have theeffect of concentrating and directing toward the well Ill the explosiveforces developed upon detonation thereof. Preferably the cavities in thecharges I3 and Ill are so arranged that the explosive forces developedupon detonation thereof are directionalized along Y I-ll in Fig. 3illustrating the cross sectional connating device or blasting machine I5of the This deviceis disposed at the earths surface at a convenientAwell known electric impulse type.

point adjacent the Wells Il) and I2. Although: the charges I3 and I4 areillustrated as being connected for simultaneous detonation, it will Y beunderstood that they may be detonated one nat a time in any desiredorderas convenience may dictate. It will also be understood that electricaldetonation of the charges is illustrated by way of example only. '.Thus,any or all of the charges may be detonated through the use of torpedobumpers, time bombs or jack equi-bs if required by the conditionsencountered. SuchV directionalization of the explosive forces may beobtained by utilizing shooting devices or charges I3 and Iii of theimproved form illustrated in Figs. 3 to 12, inclusive, of the drawings.

For the Well I0, it is desirable to use a device i3 having four or moreequi-angularly spaced cavities spaced along the sides thereof in orderto produce directionalization of the explosive forces developed upondetonation of the device in several different directions. This maybeaccomplished by using the device I3 illustrated in Figs. 3 and 4 of thedrawings. In brief, this device comprises an elongated sheet metalcontainer I5 having a column of explosive material il therein, the sidesof which are provided with a plurality of equi-angularly spaced V-shaped cavities I3 (four illustrated, but others may be added) whichextend continuously through the length of the column and projectinwardly from the outer surface thereof. Preferably the cavities I8 areformed in the sides of the explosive column I7 by providing V-shapedmetal liners I9 which are held together by means of metal assembly rings2t extending through the outer edges thereof and preferably soldered,brazed or otherwise rigidly connected thereto. These liners arepreferably self-enclosed by means of front strips and end platesfabricated thereto so that sealed cavities are provided therewithin.

The outer surfaces of each liner I9 should be in intimate contact withthe explosive material and preferably denne an angle of from 45 to 60degrees. In the assembly of the device i3, which may take place onlocation at the point of well shooting, the liner assembly is slippedinto the container I6 until the bottom end thereof engages the inwardlytapering bottom walls of the container, following which the unoccupiedspace within the container I6 is iilled with explosive materialpreferably of the gelatin variety such, for example, as or 100 percentgelatin, manufactured by E. I. Dupont de Nemours Company, Inc. After thecasing I6 is thus loaded, a detonating cap 2I may be introduced into theexplosive material preferably at the exact center thereof, i. e., alongthe longitudinal axis of the explosive column. The top of the containermay now be closed by means of a cover 22 having an opening 22atherethrough through which extend the circuit conductors 2 Ia leading tothe ignition elementof the cap 2l.

Preferably, theopening- 22a is sealed around.'

the arrows in Fig. 2 of" assaise the conductors 21a to exclude liquidfrom the container l 6. After the device is thus assembled, anddepending upon the size and weight thereof and also upon the depth ofthe well It into which it is to be inserted, the cable comprising theconductors 2Ia may be employed to lower the assembled device to thebottom of the well. Alternatively, a separate cable may be used for thispurpose.

In lieu of the elongated V-shaped liners i9.

oppositely directed conical liners of the character shown in Figs. 5 and6 of the drawings may` be disposed in the container i6 to provide rowsof conical cavities in the explosive column l1 which extendlongitudinally of the column. Preferably the conical cavity formingliners are arranged in sets of four with the liners of each set closedat their outer ends and held in assembled relationship either by meansof crossed rods 24 welded to the apexes of the liners and to each otherat the point of crossing in the manner shown in Fig. 5 of the drawings,or by means of a `ring 25 which extends through the V-related walls ofthe liners and is welded to each liner in the manner shown in Fig. 6 ofthe drawings. Y Alternatively, the cavity forming liners may take eitherof the forms villustrated in Figs. '7 and 8 of the drawings. As shown inFig. 7*, four conical shaped liners having their outer ends closed andtheir apexes joined together as by soldering, brazing or the like andextending outwardly vat ninety degrees relative to each other are formedinto one assembly of the proper diameter to t within the casing I6. Inthe structure shown in Fig. 8 of the drawings, four closed end, steerhorn-shaped liners 21 arranged in a set and having pointed ends rigidlycon nected together are used to form the four equiangularly spaced apartcavities in the explosive column I1.

When any one of the four liner constructions illustrated in Figs. 5, 6,7 and 8 of the drawings is used in loading the container i6 in themanner explained above, several sets of the liners are sandwiched inbetween the explosive material at different depths longitudinally of thecontainer as the loading operation proceeds. During this operation, careshould be exercised to maintain the cavity liners in alignmentlongitudinally of tho explosive column if it is desired that upondetonation of the column the explosive forces will be directionalized inthe four principal directions of` interest, i. e., toward the waterwells l2. Preferably, however, the liners are angularly oilset as theloading operation proceeds in order to provide all arounddirectionalization of the explosive forces in the manner indicated bythe Varrows shown in Fig. l of the drawings. Aside from the details ofthe liner constructions, the device i3 may be formed using any one ofthe linerembodiinents illustrated in Figs. 4 to 8, iaclusive, intheexact manner explained above with reference to Figs. 3 and 4 of thedrawings.

Preferably, the liners, regardless oi configuration, are formed ofnon-sparking metal, such as brass or copper, to minimize the likelihoodof inadvertent detonation of the explosive material, and have a wallthickness of the order of 0.075 inch. In lieu .oi assembling allcomponents of :the entire device i3 on location, the liners or linersubassemblies may, of course, .bepreassembled with the container I6during manufacture. nsuch case, i-t is desirable to fabricate the edges`or ends of the liners to the inner wall of the container in order -toinsure maintenance o the desired positional relationship between thecavities formed in the explosive column when the container is loadedwith explosive material.

For reasons apparent from the foregoing explanation, it is desirable toemploy explosive charges in the water wells I2 which, upon detonation,produce directionalization of the explosive energy generally toward theoil well lil. More speciically, the explosive forces should :bedirectionalized within a quadrant of about thirty degrees, the bisectingline of which passes through tho oil well iii. To this end, the linerarrangement of the explosive charge may be of the form illustrated inFigs. 9 and 10 of the drawings. As there shown, the container 16a,lwhich may be identical with the container I5 shown in Fig. 3 of thedrawings is filled with explosive material to form an explosive columnIla having conical cavities iSa formed therein along one side thereofand spaced longitudinally ofthe column. These cavities are formed byproviding conical shaped liners 2t of non-sparking znetal which extendtransversely ofthe column at spaced points longitudinally thereof andare provided with rod extensions 28a at the pointed ends thereof suchthat they may be wedged into the container lila. These liners may eitherbe xedly secured within the container ido: in the manufacture of thecontainer assembly, or alternatively may be forced into the containerduring loading thereof at the point where the well shooting operation isto 'ce carried out. Preferably they are angularly stag'- gered in themanner indicated in Fig. lo of the drawings, to point in the threedirections indicated oy the arrows radiating from each well l2 shown inFig. l of the drawings so that the desired quadrentialdirectionalization of the explosive forces is obtained. For reasonsexplained below, with these liners arranged in staggered alignmentlongitudinally of the explosive column, the explosive forces developedupon detonaticn of the column are directionalized along a quadrantbisected by a vertical plane which also bisects the aligned centercavities. Accordingly, in lowering each device id into one of the waterwells i2, care must be taken to see that the center cavities i8@ of thedevice are pointed toward the well iii as the device ill is brought toresil at the bottom of the well i2 in which it is deposited. rl"his maybe accomplished by employing a gyroscopic device of the charactercommonly employed in oil well logging work.

After 'the cavitated charges or devices i3 and ld have been deposited atthe bottoms of the wells lo and i2 with the cavities thereof properlydirected toward each other in the manner explained above and after thecircuit conductors extending to the detonating caps of the charges areproperly connected to the detonator i5, they may be detonated togetheror one at a time through appropriate operation o' the detonating devicel5. Due to the eect of the cavities provided in the charges, theresulting explosive forces are concentrated and directionalized toproduce cracking of the formation materia-l adjacent the .bottom of thewell l. Thus the cavities provided in the explosive columns 0I theshooting devices cause ie well known Monroe eiec-t to he realized.Specifically and considering one of the V-shaped cavities i8 in theexplosive column i? byV way of example, the explosive forces firsttrav-e1 perpendicularly away from the wall surface of the cavity, meetand then travel in highly -concentrated form radially outward from theaxis of the explosive column. The major portion of acsaisg the explosiveenergy is thus dissipated in this jet effect which is concentrated alonga planar path bisecting the angle of concavity. Thus in the four-cavitystructure shown in Figs. 3 and 4 of the drawings the major portion ofthe explosive energy is directed outward in the four directionsradiating from the longitudinal axis of the explosive column andbisecting the four cavity lin-ers iS, i. e., toward the water wells l2.This means that the formation material adjacent the bottom of well iiiis broken up for a substantial distance away from the bottom of the Wellit along each of four paths extending toward the water Wells I2. Fourchannels are thus effectively cut through the subsurface material forsubstantial distances away from the bottom of 'the well iii. Ifadditional cavities are provided in the explosive column,directicnalization is, of course, obtained in the o-ther directions asWell. Similarly, the directionalization of the explosive energyresulting from provision of the cavities i3d in each of the charges ifi,cause the subsurface material to be penetrated a relatively greatdistance from the bottom of each of the holes i2 generally toward the`well iii. Due to the fact only a minor portion of the explosive energyas developed by each charge iii is expended in direc--Y tions other`than within the quadrant extending toward the well id, it will beunderstood that the subsurface material outside of the quadrant is notcracked to any appreciable extent. This is cf great importance, since itminimizes the amount of water which must ,be pumped into the subsurfacestructure to produce lifting of the oil to an elevation such' that itwill now through the cracked subsurface material into the well l2 fromwhence it may be pumped to the surface. lf desired, a mechanical buffer,in the form of an air space or rock wool surrounding al1 portions ofeach explosive column except the cavitated portion, may be used tofurther minimize breaking up of the subsurface material in directionsother than toward the well H3. More specically, rock wool is preferablyused as the buffer or cushioning medium if the wells l2 are dry, and airis preferably used for this purpose if the Wells are liquid filled atthe time the described shooting steps are performed. The cushioning aircolumns may be easily provided around the non-cavitied sides of thecharges lli by employing charge containers having spaced walls definingan air space therebetween around the non-cavitied parts only of thecharges. It will thus be understood that the present inventionrepresents a distinct advance in the art of cracking the subsurfacematerial adjacent the bottom of an oil well to permit water iiooding ofthe oil-bearing structure for the purpose of lifting the oil to such anelevation as will permit its withdrawal from a Well penetrating thestructure.

Although the invention has been described above with particularreference to'increasing the permeability of the subsurface oil-bearingstructure adjacent a single well, it will be understood that it isgenerally applicable to oil eld work. Thus, in any given eld the waterwells (or alternatively exhausted oil wells which are used for pumpingwater into the subsurface structure) may be interposed between andaround the oil wells in various patterns. In such case, the particularpattern formed by the several wells should be taken into account inselecting the form of directionalization best suited to the particularsituation as well as the particular orientation whicn should be impartedto each water well charge. By so doing, shooting of the water wells maybe advantageously used to increase uid flow into several oil Wells.

Shooting devices of the character illustrated in Fig. 3 of the drawingsand equipped with cavity forming liners of the character there shown, orof one of the alternative forms shown in Figs. 5 to 8, inclusive, of thedrawings, may be employed for the purpose of shooting an oil well toincrease primary production. In such case, the same shooting techniqueis employed in so far as the construction and handling of the shootingdevice i3 are concerned. Since directionalization of the explosiveenergy along predetermined paths radiating from the axis of theexplosive column is not required, cavity forming liners of the charactershown in Figs. ll and l2 of the drawings may, if desired, be used inlieu of those described above. As there shown, the cavities areV formedby providing annular liners 29 of V-shaped cross section which arespaced apart vertically of the explosive column I1 to provide continuousannular cavities lSb of V-shaped cross section around the explosivecolumn at vertically spaced points therealong. Preferably the outersurfaces of each liner define an angle of from 45 to 6U degrees. Herealso, the liners 29 may be slipped into the container i6 as the loadingoperation proceeds. When this form of cavity is produced in theexplosive column, directionalization of the explosive energy developedupon detonation of the explosive material is eective along verticallyspaced horizontal planes rather than along angularly spaced verticalplanes. The concentrating and directionalizing effect is, however,realized in precisely the manner described above, the end result beingthat a far greater degree of penetration of the subsurface formationmaterial is obtained. With the Fig. ll cavity arrangement, thepenetration is substantially uniform in all directions radiating fromthe longitudinal axis of the borehole, an effect which is n-otobjectionable and may be desirable in certain structures.

From the foregoing explanation it will be understood that the presentinvention affords a reliable and economical solution to the problem ofshooting oil wells either for the purpose of increasing primaryproduction or the purpose of directionally cracking the subsurfaceformation material to facilitate Water flooding in carrying out wellstripping operations, or other special techniques. Thus the inventionprovides for more widespread cracking of the formation out from theborehole (and thus better permeability) thando ordinary shootingmethods, both for the outflow of iiuid from the water wells and theinflow of uid into the oil well. Further, the jet effect obtained bydirectionalizing the explosive forces precludes the possibility ofuniformly compressing the walls of the borehole to render more diicultthe flow of oil into the bottom of the well. Moreover, the high degreeof concentration and directionalization of the explosive forces insuresmuch greater penetration of the subsurface material per unit ofexplosive material used than can be obtained by conventional shootingmethods. In addition, the shooting devices, regardless of the particulardescribed embodiment thereof which may be used, are simple in theextreme and are comprised of low cost components which may easily beassembled at the point where the well shooting operation is t0 becarried out, and used by Workmen familiar 9 with the ordinary tools andtechniques of oil well and casing shooting.

While different embodiments of the invention have been described, itwill be understood that various modications may be made therein whichare within the true spirit and scope of the invention as dened in theappended claims.

I claim:

1. The method of recovering oil from a depleted producer well, therebeing a plurality of intake wells spaced laterally from said producerwell and extending to at least the depth of said producer well, whichcomprises the steps of lowering into said intake wells to points spacedlaterally from the bottom of said producer well'explosive charges havingcavities in the sides thereof for directionalizing the explosive forcesdeveloped upon detonation of said charges, positioning said charges sothat said cavities generally face the bottom of said, producer well,whereby the explosive forces developed upon detonation of said chargesare directed generally toward the bottom of said producer well,detonating said charges to open up fluid channels leading from saidintake wells toward the bottom of said producer well, thereby toincrease the permeability of the subsurface material surrounding saidproducer well, cushioning the explosive forces radiating from theexploding charges in all lateral directions other than generally towardthe bottom of said producer well, thereby to prevent the breaking up orchannelizing of the subsurface material in directions extendinglaterally from said intake wells away from said producer well and oodingsaid intake well with a pressurizing fluid which penetrates saidsubsurface material through said channels, thereby to facilitate theflow of oil into the bottom of said producer well.

2. The method of recovering oil from a depleted producer well, therebeing a plurality of intake Wells spaced laterally from said producerwell, which comprises lowering into said intake wells to points spacedlaterally from the bottom of said producer Well explosive charges havinglocalized cavities in the sides thereof for directionalizing theexplosive forces developed upon detonation of said charges, positioningsaid charges so that said cavities generally face the bottom of saidproducer well, whereby the explosive forces developed upon detonation ofthe charge in each intake well are directed generally toward saidproducer well, lowering to the bottom of said producer well an explosivecharge having cavities around the sides thereof for directionalizing theexplosive forces in directions laterally of said producer well,detonating said charges to open up fluid channels leading from saidintake wells toward the bottom of said producer well and other channelsleading from the bottom of said producer well toward said intake Wells,thereby to increase the permeability of the subsurface material betweensaid producer well and said intake wells, cushioning the explosiveforces radiating from the exploding charges of said intake wells in alllateral directions other than generally toward the bottom of saidproducer well, thereby to prevent the breaking up or channelizing of thesubsurface material in directions extending laterally from said intakewells away from said producer well, and flooding said intake wells witha fluid which penetrates said subsurface material through saidfirst-named channels, to facilitate the flow of oil into the bottom ofsaid producer Well through said other channels.

ROBERT L. KLOTZ, JR.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 6,258 Roberts Jan. 26, 18751,248,689 McAvoy Dec. 4, 1917 1,705,248 Hart Mar. 12, 1929 1,826,371Spindler Oct. 6, 1931 2,048,451 Johnston July 21, 1936 2,399,211 DavisApr. 30, 1946 2,409,848 Greulich Oct. 22, 1946 2,415,814 Davis Feb. 18,1947 2,494,256 Muskat Jan. 10, 1950 FOREIGN PATENTS Number Country Date28,030 Great Britain 1911 113,685 Australia Aug. 28, 1941 OTHERREFERENCES The Shaped Charge, by Torrey, in The Explosives Engineer,July-Aug. 1945.

